During the scuffle, William dropped the key to their Troll's Cave, which contained all manner of treasure plundered from the trolls' victims. Bilbo Baggins recovered the key, allowing the company to claim the treasure in its entirety, including several fine Elvish blades. Glamdring went to Gandalf, while its mate Orcrist was claimed by Thorin Oakenshield. Bilbo, too, claimed a blade: merely a dagger by the standards of Men or its original Elvish makers, and but a tiny pocket-knife for the trolls whose hoard it was found in, but it made an excellent short sword for a Hobbit. [1]

When Bilbo was captured by goblins while crossing the Misty Mountains, the goblins failed to notice the weapon simply because Bilbo wore it inside his breeches.[2] When Bilbo was separated from the others during their escape, this allowed him to rely on the dagger's glowing blade to light his way, as well as use it to keep a hungry Gollum at bay while he tried to find his way out of the labyrinthine tunnels in the roots of the mountains.[2]

The weapon remained nameless until the company reached Mirkwood and, deep in the darkness, Bilbo and his companions were beset by the forest's Spiders. Awakening to find himself half-cocooned, Bilbo used the dagger to free himself and slay his attacker, the first time he had used it in battle. The act prompted him to name the weapon with the words, "I will give you a name, and I will call you Sting." [3] Bilbo used the newly-christened Sting to cut the spiders' silk to free his companions, and during the ensuing battle, utilized it in combination with the magic ring he had found in Gollum's cave, thrown rocks, and hurled insults to help the venom-weakened dwarves fight their way out of the spiders' nest. [3]

As a consequence of his centuries of corruption under The One Ring's influence, Gollum feared weapons of Elvish make like Sting, which made the knife a factor in aiding Frodo in temporarily taming the wretched creature. It also helped Frodo and Samwise Gamgee escape from the lair of the terrible Shelob in Cirith Ungol, and during the ensuing battle, even after paralyzing Frodo, the massive spider met its match in a determined Samwise Gamgee and learned how the Elvish weapon earned its name. Still armed with Sting, Sam stormed the Tower of Cirith Ungol in order to rescue Frodo, though he found little in the way of a fight, as the tower had seen a battle between its own forces over Frodo's mithril-mail coat.

After the defeat of Sauron at the end of the Third Age, when both Bilbo and Frodo sailed across the sea to the Undying Lands, Sting remained with Sam. He may have taken it with him when he, at last, followed them as was his right as the last remaining Ring-bearer, or it may have remained as an heirloom of the Gardner Family.

Sting had the (apparently) magic ability to detect the presence of goblins in its vicinity. When Orcs were nearby, it glowed blue, as Bilbo noticed when alone in the dark just prior to meeting Gollum.[2] This ability was used several times by Frodo and the Fellowship such as when the group encountered Orcs in the mines of Moria and by Aragorn upon the Fellowship's arrival at Parth Galen.[5]

Sting also performed better than ordinary weapons in combat and against odd materials; it cut through the webs of giant spiders easily, whereas the blade that Sam brought from the Barrow-downs failed to cut through Shelob's webs.[6] During the Battle of the Chamber of Mazarbul, Boromir's sword glanced off of the hide of a troll, but Sting was able to deal a painful wound.

Sting has a distinctive shape, with a vaguely leaf-shaped blade, round, ball-shaped pommel, featureless black hilt, and a unique guard sporting a ring in the front that the wielder's finger slips into when grasping the hilt. This version of Sting glows bright white, not blue as in the books and most other adaptations. Notably, following the Rankin/Bass adaptations' pattern of not explicitly showing violence, Sting is not shown stabbing or slashing its victims; instead, a strange fly-eye like effect is shown when Bilbo slays the giant spiders in Mirkwood, an effect that is oddly repeated when he knocks another spider off of a branch with a rock.[7]

Sting's appearance is broadly similar to that in Rankin/Bass' earlier film, with some alterations; notably, the shape of the blade is changed from vaguely leaf-shaped to stout and straight-bladed, and the hilt is no longer a featureless black, but is now adorned with intricate designs.[8]

Sting is leaf-shaped. Upon its crossguard are engraved the Sindarin words:

Maegnas aen estar nin dagnir in yngyl im

Which is translated "Maegnas is my name, I am the spider's bane" (Maegnas is neo-Sindarin for "Sting")

Since the sword was given a name by Bilbo and the inscription mentions Bilbo's adventure, it can be supposed that the Elves engraved the letters on the ancient sword while Bilbo was in Rivendell. This is supported by The Hobbit (film series) in which Sting appears plain, without any writing.

Unlike the book, Sting is first seen in the Dream World stage, a sort of tutorial wherein Bilbo, after fainting during the Unexpected Party, dreams he is at the Battle of Five Armies and must fight his way through a few waves of goblins before being overwhelmed by Bolg and his guard, startling awake, and continuing the story.[9] After Bilbo awakens, Sting is not seen again until the end of the Troll-Hole stage, which takes place after the encounter with Tom, Bill, and Bert like in the book. Unlike in the book, where Bilbo does not name Sting until he is in Mirkwood, he gives it a name almost immediately.[10]